This research project addresses an important problem faced by the chemical and drug industries-their requirement to evaluate the DNA damaging potential of ever increasing numbers of new chemical entities in shorter periods of time. This situation presents opportunities for small businesses that are able to provide solutions to these challenges. Our proposal answers industry's need for higher throughput toxicity assessment through the development of an automated in vitro chromosomal damage assay. Chromosome damage will be quantified by flow cytometric micronucleus measurements. Importantly, the methodology that will be developed over the course of this project not only represents a high volume genotoxicant screening system, but also one that can be configured to identify agents which protect against chromosomal damage, i.e. biological response modifiers (BRMs). BRMs provide chemo- or radio-protection benefits that hold great promise in several important arenas, including treatment of cancer patients, protection of our troops during times of war, and for treatment of civilian victims of chemical or radiological terrorist attacks. The proposed Phase II experiments will initially focus on developing the methodologies that will allow us to incorporate automatic liquid handling devices into a miniaturized assay. By eliminating transfer steps and other labor-intensive tasks, the assay will meet the specifications of pharmaceutical and chemical companies that have high volume testing requirements. Once this is established, we, and our collaborators in the pharmaceutical industry, will evaluate a panel of genotoxicants and non-genotoxicants, thereby providing information regarding assay portability, sensitivity, and specificity. Additionally, two other lines of investigation will be undertaken: evaluation of the HepG2 liver cell line; and utilization of the micronucleus scoring assay for the purposes of radioprotectant identification/characterization. Ultimately, optimization and validation of this screening assay will help chemical and drug companies allocate their resources to their most promising candidates, eliminating hazardous entities early in development. Furthermore, by aiding in the identification of next generation BRMs, cancer patients and armed forces will benefit from the availability of chemo- and radio-protectant drugs. Along with recent advancements in the fields of molecular biology, chemistry and medicine comes an ever- increasing number of new and potentially helpful drugs and industrial chemicals. The ability of pharmaceutical and chemical companies to prioritize these agents in terms of safety and efficacy is often hampered by the use of outdated methods and/or technologies. This proposal addresses the stated need for an automated and miniaturized in vitro micronucleus assay designed to rapidly and efficiently detect the chromosome damaging potential of drugs and chemicals. In addition, this assay can be used to investigate agents designed to ameliorate the effects of radiation exposure, e.g. biological response modifiers. [unreadable] [unreadable] [unreadable] [unreadable]